much. Let's dig in with Martha Raddatz, our counterterrorism expert, Richard Clarke, who directed things like this at the highest levels with many presidents. And retired general John Allen. Let me begin with you. You're really sounding the alarm here. You call Isis a clear and present danger. Say we must act now to destroy it. The big question. How? It will require a comprehensive approach. It has to be more than simple pinpoint attacks. On key Isis locations, just security locations in and around dams. Supporting fire. It requires a comprehensive approach. Got to be a regional approach, a coalition approach. While some aspect of the coalition can be focused on the humanitarian relief of the populations that have been put to foot and caused to evacuate the areas where they have lived for centuries and so on, it will require a comprehensive approach to strike Isis throughout the network of the organization. Some of that is in Iraq. A lot of that, particularly the support areas, are inside Syria. So that means hitting inside Syria, I imagine. You say it will take a coalition. Could that include some kind of cooperation and coordination with the government of Syria, the regime, the Assad regime and the government of Iran? I think that the actions we take, may, in fact, be not in coordination, necessarily, but provide an opportunity for coordinated effort. But we don't share any values with the Iranian regime or the Syrian regime. The Syrians, in fact, are one of the principle reasons that Isis has had the opportunity to incubate to this point to the level that it is. To the threat that it has become. The Assad regime has turned a blind eye to the development of Isis and permitted them, ultimately to attack that element that we have been and ought to beupporting in Syria, the free Syrian movement. The free Syrian movement is caught between two very tough regime efforts and Isis efforts to eliminate its existence. Some have said the effort you're talking about will take up to 10,000 new advisers and special operations forces on the ground. Is that what it's going to take? It will take more than what we're doing right now. There's just no question of this. We need to give the American public more clarity in terms of commitment, solely using the term boots on the ground. We have been clear we don't want to put American maneuver forces necessarily, conventional maneuver forces back on the ground. But we have significant capabilities. To provide special operators into these formations, both at the tribal level, some of the more recently emerging Sunni conventional forces appears in northwest Iraq. The free Syrian army. And Sunni tribes in Syria. There doesn't have to be a solely American force. There are plenty of special operations capabilities we have built up over the last 13 years in Afghanistan that permit us the capability with allies and partners both internationally and in the region, to provide significant special operations advice, support, and capabilities to the wide-ranging elements we can bring to bear to be the foot soldiers in this campaign. Where American firepower with American advice can be brought to bear to attack this network. Across the entire breadth. Not just in Iraq. Across the entire breadth regionally. This is a regional problem. Not an Iraqi problem. Not a Syrian problem. Thank you for your time. Let's bring that to Martha Raddatz. You've been reporting the white house, the administration, what they're considering. Are they going in the direction general Allen advocates? Well, it doesn't seem like they're going in that direction. I think they are going in the direction that they might do more air strikes in Syria. What general Allen said, it makes me think back what the Obama administration wanted. They wanted 10,000 troops to remain in Iraq. Not combat troops. Military advisers, special operations forces to watch the counterterrorism effort. Perhaps they would go that way. It would be a tough one. And Richard Clarke, you saw general Allen when I asked him about cooperation with Iran and Syria. He almost gulped right there. He doesn't want to say the enemy of our enemy is our friend. But we're going have to work with them, aren't we? We have to make a choice. If we want to eliminate Isis, we are going to have to deal with people we don't like.qbqç the president said we wanted Assad out. We're going to have to say something to the Syrian government if we're going to start bombing in Syria. If we're going to get rid of Isis, we're going to have to start bombing in Syria. Stand by here. I want to bring in Michael

This transcript has been automatically generated and may not be 100% accurate.

{"id":25104118,"title":"Ret. Gen. John Allen: Need Comprehensive Approach to Destroy ISIS","duration":"4:50","description":"The former U.S. commander in Afghanistan on how the U.S. should tackle the threat from ISIS.","url":"/ThisWeek/video/ret-gen-john-allen-comprehensive-approach-destroy-isis-25104118","section":"ThisWeek","mediaType":"Default"}